Although this year’s "Lake Michigan marbles" are much bigger than usual, Myers said they're not a new phenomenon.

Ice chunks form along the shore, get churned back and forth by the waves and grow slowly in the just-below-freezing water, which also helps to smooth the boulders, she said.

"The Great Lakes create their own weather," she said, adding that the boulders aren't the only interesting ice creations at the park. There are also ice caves and large icicles most years, she said.

"It's a whole new world in the winter on the Great Lakes," she said, through a laugh.

The park -- and the ice boulders -- can thank resident Leda Olmsted for the attention.

She was on a walk with her dog last week when she noticed rows and rows of icy boulders. She snapped photos using her phone, posted them on her Facebook page and was soon swarmed with media requests.

"There was just massive, perfectly round, smooth ice balls for as far as I could see," Olmsted told Michigan's 7 & 4 News, which posted a video of the ice boulders. "And I was just astonished. I couldn’t believe ... I’d never seen anything like it before."

For Olmsted, the attention was something of a vindication.

"I've had questions like, 'Why do you live there? It's so gray and cold and there's nothing to do,'" she said. "But if you bundle up and go outside, it's literally one of the most beautiful things you've ever seen."